How to Configure IS-IS in GNS3

In the previous posts, we explained the IS-IS routing protocol in detail. We recommend you to read those posts if you missed. In this post, we will learn how to configure IS-IS on Cisco router using GNS3.

To configure IS-IS routing protocol, we will use the following network topology. In the following network topology, R1 and R2 are connected through the Fa0/0 interfaces, while R2 and R3 are connected through the Fa0/1 interfaces.

Steps to Configure IS-IS

Let’s begin how to configure IS-IS on Cisco router. To configure IS-IS, you need to perform the following steps:

On R1, execute the following commands to assign 1.1.1.1/24 IP address to the Loopback0 interface.

Verify IS-IS Configuration

Once you have configured IS-IS on all the routers, now verify your configuration. To verify the IS-IS routing configuration, execute the show ip route command and verify the routing table. You should be able to see the routes added by the IS-IS routing protocol. In addition, you can also test the network connectivity between R3 and R1 by executing the ping 1.1.1.1 command on R3.

In the following figure, you can see the routing information added by the IS-IS routing protocol.

One more important command you need to consider is show clns neighbors. It displays the IS-IS neighbor routers. In the following figure, you can see that R2 has two neighbors R1 and R3. R1 is connected to R2 via the Fa0/0 interface and R3 is connected to R2 via the Fa0/1 interface.

In this post, you have learned how to configure IS-IS on Cisco routers using GNS3. We would love to hear your suggestions. In the upcoming posts, we will configure IS-IS using a complex network topology.